Asymmetric Reduction of Keto Acids by Use of Bakers' Yeast

（1）使用含有氧化还原酶的面包酵母匀浆进行不对称还原使用NADPH作为辅酶，用匀浆还原作为底物的脂肪族δ-酮酸。产物具有与来自完整细胞的产物相同的构型（R）。两种产物的% ee也> 98%ee。由于匀浆的物质平衡更好，因此表明底物在完整细胞中损失了一部分。然而，没有得出关于基质或产品通过细胞壁或细胞膜的渗透是关键的可能性的结论。（2）金属盐的影响添加浓度为1.5mol/L的MnCl_2可使面包酵母的还原率从64%提高到84.89%。这一结果只在底物n-C_5 H_<11>COCH_2CH_2CO_2 H中发现，这是一个有趣的但不能解释的现象。（3）用面包酵母不对称还原多官能β，δ-二酮酸主要的还原产物是β-酮-δ-羟基酸，发现它不能进一步还原成β，δ-二羟基酸。得到β-羟基δ-酮酸作为次要产物，发现其相当容易还原成β，δ-二羟基酸。所有手性碳原子的构型均为R，% ee&gt; 99%ee。δ-羟基化合物可环化为β-酮或β-羟基δ-内酯。（4）利用面包酵母不对称还原β-氯-γ-酮酸RCOCHClCH_2CO_2H还原为相应的仲醇：R=CH_3，构型=S，产率50 - 60%，&gt; 99%ee; R=C_2H_5，S，产率10%，68%ee; R=n-C_3 H_7，R，产率20%，61%ee; R=n-C_4 H_9，产率<13>20%，&gt; 98%ee。

(1)Asymmetric Reduction by Use of Bakers' Yeast Homogenate Containing OxidoreductaseAliphatic delta-keto acids as substrate were reduced with the homogenate by use of NADPH as coenzyme. The products had the same configuration(R)as that for the products from the intact cells. The % ee was also>98% ee for both products. Since the material balance was better for the homogenate, it was suggested that the substrate was party lost in intact cells. However, no conclusion was derived about the possibility that the permeation of the substrate or the product through the cell wall or membrane is critical.(2)Effects of Metal SaltsAddition of MnCl_2 at a concentration of 1.5 mol/L enhanced the yield of bakers'yeast reduction from 64% to 84 89%. This result was found only for the substrate, n-C_5H_<11>COCH_2CH_2CO_2H, which is interesting but not explicable.(3)Asymmetric Reduction of Polyfunctional beta, delta-Diketo Acid by Use of Bakers' YeastThe main reduction product was beta-keto delta-hydroxy acid, which was found not to be reduced further to beta, delta-dihydroxy acid. beta-Hydroxy delta-keto acide was obtained as a minor product, which was found to be rather readily reduced to beta, delta-dihydroxy acid. The configuration was R for all chiral carbon atoms and the % ee was>99% ee. The delta-hydroxy compounds can be cyclized to beta-keto or beta-hydroxy delta-lactones.(4)Asymmetric Reduction of beta-Chloro gamma-Keto Acid by Use of Bakers' YeastRCOCHClCH_2CO_2H was reduced to the corresponding secondary alcohol : R=CH_3, config=S, 50 60% yield, >99% ee ; R=C_2H_5, S, 10%, 68% ee ; R=n-C_3H_7, R, 20%, 61% ee ; R=n-C_4H_9 n-C_6H_<13>, R, 20%, >98% ee.